The invention relates in general to electronic printers and copiers, and in particular to printers and copiers where both the front and back surface of a paper document are to be printed.
When using electronic cash registers and point of sale printers, it is often necessary to print on the front and back surface of a document, such as a check. This is sometimes accomplished by a salesperson physically inserting a check into the path of a print head so that one side can be printed, removing the check, turning it around and reinserting the other side of the check so the other side can be printed. This procedure is time consuming and often the sales person inserts the wrong side of the document into the path of the printer head.
Some cash registers and point of sale printers, known as xe2x80x9cduplex printersxe2x80x9d are capable of printing on both sides of a document without the need for human intervention. Depending on the design scheme, duplex printers use one or multiple print stations. Duplex printers that use a single printer station physically turn the document so that printing occurs sequentially on both surfaces of the document. A turning mechanism must be supplied to turn or flip the document. Such a mechanism was disclosed in U.S. Pat. No. 5,865,547, issued Feb. 2, 1999 to Harris. These mechanisms are relatively more expensive. Furthermore, turning or flipping the document greatly increases the probability that a paper jam will occur. As such, these mechanisms often have relatively higher maintenance costs.
Another approach is the use of two print stations. However, the cost of the printer or register is significantly increased because the print station is typically one of the more expensive parts of the printer. Furthermore, the use of two print stations increases the overall failure rate of the printer and increases maintenance costs.
What is needed, therefore, is a device which economically and reliably allows printing on both sides of a document without the use of a turning mechanism or two printer stations.
The previously mentioned needs are fulfilled with the principle of the present invention. Accordingly, there is provided, in a first form of the present invention a printing apparatus consisting of a print head, a transfer surface and a medium path such that as the medium is transported along the medium path the print head prints a first image on the transfer surface, then sequentially prints a second image to one face of a medium while the transfer surface is transferring the first image to the other face of the medium by pressing the transfer surface against the medium.
A method for printing is also disclosed comprising the steps of printing a first image on a transfer surface, printing a second image directly onto one face of the medium, then transferring the first image onto the other face of the medium.
These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to note the drawings are not intended to represent the only form of the invention.